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(No Model.)

W. s. DAVIS.

TELEPHONIG TRANSMITTER.

No. 305,901. Patented Sept. 30, 1884 Fig.1

extended to the other hinge.

Priest WILLIAM SULLIVAN DAVIS, OF LOWELL, MASSACHUSETTS, ASSIGNOR OFONE-HALF TO JONATHAN KENDALL AND GEORGE M. KENDALL, BOTH OF SAME PLACE.

TELEPHONIC TRANSMlTTER.

SPECIFICATION forming part of Letters Patent No. 305.901, datedSeptember 30, 1884.

Application filed February 4, 1884.

To aZZ whom it may concern: Be it known that I, WILLIAM SULLIVAN DAVIS,of Lowell, in the county of Middlesex, of the Commonwealth ofMassachusetts, have inventeda new and useful Improvement in TelephonicTransmitters or Microphones; and I- do hereby declare the same to be de'scribed in the following specification and represented in theaccompanying drawings, of no which- Figure l is a view of my improvedarticle as open or with the cover of its case turned back. Fig. 2 is alongitudinal section of it. Fig. 3 is a transverse section taken length-I 5 wise through the two electrodes.

' My invention, the nature of which is defined in the'claim hereinafterpresented, relates specially to the well-known Blake transmitter, ormicrophones of like character.

In carrying out my said invention I have combined with a Blaketransmitter a vibratory supporting disk or diaphragm having a diameterlonger than that of the sustaining ring of the diaphragm of thetransmitter, such additional diaphragm being fastened to the said ring,and arranged concentrically therewith, and encompassed bya rubber ring,in turn inclosed in a metallic one, which is fastened to. the inner faceof the cover of the case.

In the drawings, A denotes the said case, and B its cover, the latterbeing secured to the case by metallic hinges a 0. Within the case is theusual induction-coil,C, and

3 besides such I place in such case a small electric or galvanicbattery, D, having one of its current-wiresviz., b-connected with one ofthe hinges a a, and the other, 0, with the induction-coil, a wire, 0,from such coil being Wires (1 and e extend from the hinges to the twoelectrodes f and g, arranged as represented with the diaphragm h of theBlake transmitter. This diaphragm is encompassed by a rubber ring, i,

5 fitted into a metallic ring, k.

To the front side of the ring k, I fasten concentrically to the saidring an auxiliary diaphragm, Z, longer in diameter than the ring 7t, andencompassed by a rubber-ring, m, which in turn is surrounded by asupporting metallic allow them to properly vibrate.

(X0 model.)

'ring, a, fastened to the inner face of the cover of the case. There isbetween the auxiliary diaphragm and the said cover ashallowchamher, 0,provided with a mouth, 1), as shown. There is also a shallow chamber, 0,between the two diaphragms, such chambers being to A series of springs,q, fixed to the metallic ring n,extends to the inner face of the saidauxiliary diaphragm,upon which the springs at or near o0 their free endsbear. The said springs are to keep the diaphragm in position in itsencompassing riugs, and to allow it to vibrate as may be required. Theauxiliary diaphragm, combined and arranged as described with thetransmitter or microphone and its case, is to prevent the transmitterfrom jarring or breaking up, as telephonists express the jarring soundproduced by one electrode on the other while vibrating when the partyspeaking in front of the mouth of the transmitter is close thereto. Bythe auxiliary diaphragm the main diaphragm and electrodes are vibratedsimultaneously, and become so insulated from the voice of a speaker asto be vibrated thereby only through the auxiliary diaphragm, the jarringof the electrodes being thereby prevented, as I have found in practice.Furthermore, by having to the transmitter the auxiliarydiaphragm,arranged as described, I can use to the mouth a speaking-tubeyvithout causing any of the said jarring or breaking up, and thus canincrease the volume of sound, so as to render the speech of the operatorto be heard through the telephone to much greater certainty andadvantage. \Vith the auxiliary diaphragm a stronger battery can be usedthan can with the transmitter without such diaphragm, and therefore thetelephonic current can be worked to better advantage. By having thebattery within the case of the transmitter the electrical current to theelectrodes meets with less resistance than would follow were the batteryout of the case. Other advantagesarise from 5 having the battery withinthe case of the transmitter.

In Fig. l the wires for connecting the indilation-coil with thetelephone circuit-wires are shown at d and e.

I 013111115 larger sustaining-ring, arranged in and sup The combinationof theease the diaphragm, ported by the said case, all being substan andthe electrodes of a telephonic transmittially as set forth.

ter or microphone with an auxiliary or ad- \VILLIAM SULLIVAN DAVIS. 5ditional diaphragm'larger in diameter than \Vitnesses:

the main diaphragm and its sustaining-ring, R. H. EDDY,

and fixed to the latter and to another and 1 E. B. PRATT.

